Business Wire - June 23, 1999
In a time of rising HIV drug resistance and increasing treatment choices, use of PhenoSense HIV may help physicians and patients make optimal therapeutic choices and avoid treatment failures caused by drug resistance.
PhenoSense HIV directly measures the sensitivity or resistance of a patient's virus to each of the currently available antiretroviral drugs for HIV, providing highly accurate, reproducible, and individualized drug susceptibility information in two weeks, rather than the nearly 4-6 weeks for other currently available phenotypic resistance tests. The substantial advantage in turnaround time provided by PhenoSense HIV makes phenotypic HIV resistance testing a practical tool for physicians.
"We are pleased to announce the commercial availability of ViroLogic's first assay," said Martin Goldstein, President and Chief Executive Officer of ViroLogic. "The novel technology offered in PhenoSense HIV presents physicians and patients with a considerable advance in dealing with the growing problem of HIV drug resistance. Using PhenoSense HIV to guide treatment decisions may lead to improved outcomes for patients and cost savings for payers."
The Growing Problem of HIV Drug Resistance
While combination antiretroviral therapy has produced tremendous benefit for many HIV patients, treatment failure now affects a growing proportion of patients receiving therapy. Many failures are linked to the increasing emergence of drug-resistant HIV, which is caused by the virus' extremely rapid rate of replication and mutation. In addition to affecting many patients extensively treated with antiretroviral drugs, drug-resistant HIV may also be contracted by newly infected individuals.
Use of HIV drug resistance testing can help physicians make informed treatment choices for heavily pre-treated patients failing HIV therapy and newly infected patients who are considering beginning antiretroviral therapy. HIV drug resistance testing can be used to optimize antiretroviral therapy, provide cost-effective individualized treatment strategies that may result in improved long-term suppression of HIV, and help prevent the development of drug resistance.
"HIV drug resistance testing is playing an increasingly important role in the clinical management of a growing number of patients," noted Dr. Robert Schooley, a professor at the University of Colorado and a member of ViroLogic's Scientific Advisory Board. "Many experts believe that phenotypic resistance testing is the most sophisticated and useful diagnostic tool available to help guide HIV treatment choices."
Advantages Over Genotypic Testing
The direct measurement of drug susceptibility provided by PhenoSense HIV may also present a number of advantages over another form of HIV drug resistance testing, genotypic testing.
Genotypic assays employ an indirect method of resistance testing by searching for genetic mutations in a patient's HIV that are already known to confer resistance. Interpretation of test results is often difficult, requiring analysis from expert scientists, as many mutational patterns are complex and incomplete. Furthermore, the advent of new HIV drugs and drug combinations, along with the emergence of new mutations, suggest that this indirect measurement may not provide sufficient information to predict or detect all patterns of drug resistance.
PhenoSense HIV, however, directly measures the sensitivity of a patient's HIV to all currently available antiretroviral drugs. PhenoSense HIV measures the concentration of a drug required to inhibit HIV reproduction by defined amounts, typically 50%, referred to as the inhibitory concentration, or IC50. These data are familiar and easy-to-understand since physicians have been using susceptibility data to guide antibiotic treatment of bacterial infections for nearly fifty years.
Pharmacoeconomic Model Supports Use of PhenoSense HIV
A pharmacoeconomic study found that use of PhenoSense HIV saved money and delayed treatment failure in each of six different treatment scenarios analyzed.
PhenoSense HIV is also currently being used in a series of retrospective and prospective clinical trials, both for pharmaceutical companies and other organizations, including the AIDS Clinical Trials Group (ACTG) and California Collaborative Treatment Group (CCTG).
How PhenoSense HIV Works
PhenoSense HIV employs nucleic acid amplification to derive HIV-1 protease and reverse transcriptase sequences from a patient's plasma sample. A resistance test vector is constructed by incorporating the patient-derived segment into a viral vector with an indicator gene, such as firefly luciferase, inserted within a deletion in the HIV-1 envelope gene.
The population of resistance test vectors from a given patient is tested in the lab against increasing concentrations of each of the available antiretroviral drugs, and the resulting data are plotted as an inhibition curve, which is compared to that of a drug sensitive control virus for each drug. If more drug is required to inhibit the patient's virus than the drug sensitive control virus, the patient's virus has reduced susceptibility to that drug.
PhenoSense HIV is considered to be highly accurate. In more than 95% of tests performed, IC50 measures varied less than 2.5-fold. The assay is performed in the ViroLogic Clinical Reference Laboratory, which has met the regulatory requirements of the Clinical Laboratory Improvement Act (CLIA) as well as those of several states that have enacted their own regulatory standards. ViroLogic's laboratory has received CLIA certification and is licensed by the states of California and New York.
Availability
PhenoSense HIV is available in a Comprehensive Panel that provides resistance information on all available HIV antiretrovirals. In addition, in an effort to reduce costs to patients, the test is also available as a Select Panel that provides patient resistance data on the most frequently prescribed antiretrovirals. Care providers seeking more information about ordering a PhenoSense HIV assay may call ViroLogic at 800/777-0177.
About ViroLogic
ViroLogic, a privately held South San Francisco-based biotechnology company, is a leader in the development of novel therapy guidance tools to enable patients, physicians, and medical reimbursers to make rational treatment decisions in the management of viral diseases and cancer. The Company's proprietary technology is also being used in the fields of viral pharmacogenomics to identify, analyze, and select new drug candidates for treating viral diseases and cancer, and in disease management through the development of algorithms to analyze and mine the extensive information accumulated by the Company.
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CONTACT: ViroLogic Sidney Ho, 650/635-1100, Ext. 206 sho@virologic.com
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